Answer:
[tex]3.27\cdot 10^6 V/m[/tex]
Explanation:
In order to balance the weight of the sphere, the electric force must be equal in magnitude to the weight of the sphere:
[tex]F_E = qE=mg[/tex]
where
[tex]q=3.0nC=3.0\cdot 10^{-9} C[/tex] is the charge of the sphere (we can ignore the sign, since we are only interested in the magnitude of the force
E is the strength of the electric field
m = 1.0 g = 0.001 kg is the mass of the sphere
g = 9.81 m/s^2 is the gravitational acceleration
Solving the equation for E, we find the strength of the electric field:
[tex]E=\frac{mg}{q}=\frac{(0.001 kg)(9.81 m/s^2)}{3.0\cdot 10^{-9} C}=3.27\cdot 10^6 V/m[/tex]
